This invention relates generally to the production of electron tubes and particularly to a manifold system for evacuating such tubes.
One of the final steps in producing electron tubes is evacuation of the tubes. To this end, every tube is provided with a narrow, hollow tubulation which is an integral part of the tube envelope. During evacuation, the tubulation is coupled to an evacuation device and the gasses within the tube are pumped out to permit operation of the tube. In the prior art, the evacuation device typically is a glass cylinder which is connected to a evacuation pump. The glass cylinder includes a number of small glass tubules which extend radially from the cylinder and which communicate with the inside of the cylinder. Typically, the small tubules have essentially the same external and internal diameters as those of the tubulations of the tubes being evacuated. The tubules and the ends of the tubulations are connected by heating them to form molten glass so that the glass hardens during cooling and the tubulations are hermetically coupled to the tubules. The tubes are then pumped down to remove the gases within the tubes. After the desired degree of evacuation is obtained, the tubulations are individually heated into a molten state. Atmospheric pressure acts on the molten glass and collapses the glass to separate the tubulations from the tubules and to hermetically seal the tubulations. After all the evacuated tubes are removed from the tubules of the evacuating cylinder, the remainders of the tubulations are removed from the tubules using glass cutters.
Evacuation cylinders of the type described are effective in evacuating tubes but suffer several disadvantages. Firstly, the evacuating systems are made of glass and thus are quite fragile. Also, the evacuation systems are made of blown glass and therefore their manufacture requires great skill. Additionally, coupling the tubulations to the tubules requires great skill, is a time consuming task and the separation of the tubulation remainders from the tubules requires substantial skill to avoid damage to the evacuating system. Furthermore, the tubulations and tubules are rigidly coupled and therefore a slight jar can break a tubulation and ruin all tubes which are coupled to the evacuating cylinder. For these reasons there is a need for a rugged, electron tube evacuating manifold system which is easy to manufacture and to use and which does not require glass blowing and glass handling skill in the manufacture and use thereof. The present invention fulfills these needs.